According to the USDA, boiling beans significantly reduces their calcium content. If true, why?
Calcium is a metal which shouldn’t be destroyed by heat. Is there something else going on?
Calcium is water soluble in most natural forma, so it is likely being lost to the water you boil the beans in. In theory you could probably get this calcium by simply drinking the bean water, but this is not expected and with some beans I believe it is not recommended.
Legumes are filled with anti-nutrients and soaking, boiling, and cooking them greatly neutralizes these anti-nutrients so it is overall very worthwhile to lose some raw nutrients in the preparation of your food if it increases the overall absorbability of nutrients that remain.